The present invention relates to motors, and more particularly to a motor in which brushes feed a current to a commutator of a rotor so as to produce an electrical field around the rotor, and the rotor is allowed to rotate by placing it in interaction with the magnetic field formed by a stator.
Small brush-type motors are used as part of electrical equipment in automobiles, such as an electrically controlled mirror or a power window.
In this kind of motor, connection between a brush and an external circuit is conventionally achieved via a brush arm and a terminal component. A brush arm is formed of a conductive material and has a brush fixed to the end thereof. The other end of the brush arm is fitted, for example, to a motor case. When a current is applied to the brush, the brush arm operates so as to press the brush against the commutator. The terminal component, which is fabricated separately from the brush arm, is connected to the brush arm at one end, and to an external circuit terminal extending from the external circuit at the other end, so that the connection between the brush arm and the external circuit terminal is achieved. In some motors of this kind, a thermistor having a positive temperature coefficient (that is, the thermistor which exhibits an increase in its resistance as the temperature rises) and a current feed line are connected in series in order to prevent the coil of the rotor from being burned by being overheated due to an excess current resulting from an overload or the like.
In a brush-type motor and a thermistor having a positive temperature coefficient, the thermistor having a positive temperature coefficient is connected between the brush arm and the terminal component so as to make the motor as compact as possible.
However, the construction of the conventional motor in which the external circuit terminal and the brush are connected to each other via separately fabricated parts, that is, the brush arm and the terminal component, calls for holding the brush arm and the terminal component in their respective positions and providing necessary connections individually. Hence, inconvenience is encountered during the assembly. Since a space for accommodating the terminal component is required, an effort to make the motor more compact is thwarted, and the cost of producing the motor tends to be high. Since a thermistor is required in addition to the brush arm and the terminal component in a brush-type motor having a thermistor built in, the overall construction becomes even more complex. This results in the increase in possible causes of failure, the increase in the production cost, and inconvenience encountered during the assembly.